A conventional switch device, especially for those switches using bimetallic plate to prevent it from being burned when the switch device is overloaded, generally includes a bi-metallic plate which is deformed when there is overload so as to separate the two contact points respectively located on the bi-metallic plate and one of the two terminals. Some inherent shortcomings for these conventional safety switch devices are found. Firstly, there are too many parts involved in the safety switch device and it is time consuming to assemble the switch device, and this increases the cost of the products. Secondly, the parts may be arranged inaccurately to impact the deformation of the bi-metallic plate. Once the bi-metallic plate is deformed to cut off the circuit, because of the improper arrangement of the parts as mentioned above, the bi-metallic plate could deform to re-connect the two contact points to connect the circuit again. Thirdly, because of the inaccuracy of the deformation of the bi-metallic plate, the switch member does not switch to the “OFF” position after the bi-metallic plate is deformed to cut off the circuit. Therefore, the user cannot distinguish the status of the switch device by the position of the switch member.
Therefore, it is desired to have a switch device wherein the bi-metallic plate is well positioned when the switch device is in “ON” and “OFF” positions.